U.S. patent number 6,274,660 [Application Number 09/243,948] was granted by the patent office on 2001-08-14 for coating composition and its use and process for its preparation.
This patent grant is currently assigned to BASF Coatings AG. Invention is credited to Hubert Baumgart, Thomas Farwick, Edeltraud Hagemeister, Peter-Heinz Rink, Peter Schwab, Edgar Zeller.
United States Patent |
6,274,660 |
Zeller , et al. |
August 14, 2001 |
Coating composition and its use and process for its preparation
Abstract
The present invention relates to a coating composition featuring
increased solids contents, which comprises at least one polyol I
obtainable by subjecting at least one oligomer of the general
formula I in which R=--(--CH.sub.2 --).sub.m --, in which the index
m is an integer from 2 to 6, or ##STR1## in which X=--CH.sub.2 --
or an oxygen atom R.sup.1,R.sup.2,R.sup.3 and R.sup.4 independently
of one another=hydrogen atoms or alkyl; and the index n=an integer
from 1 to 15; to hydroformylation and reducing the resultant
aldehyde-functional products I to give the polyols I, which, if
desired, are subjected to partial or complete hydrogenation.
Inventors: |
Zeller; Edgar (Mannheim,
DE), Schwab; Peter (Bad Durkleim, DE),
Rink; Peter-Heinz (Munster, DE), Baumgart; Hubert
(Munster, DE), Hagemeister; Edeltraud (Greven,
DE), Farwick; Thomas (Billerbeck, DE) |
Assignee: |
BASF Coatings AG
(Muenster-Hiltrup, DE)
|
Family
ID: |
26043772 |
Appl.
No.: |
09/243,948 |
Filed: |
February 3, 1999 |
Current U.S.
Class: |
524/379;
427/385.5; 427/388.1; 427/389.7; 427/391; 427/393.5; 427/395;
524/111; 524/380; 524/381; 524/386; 524/388; 524/389; 524/391;
524/502; 524/513; 524/514 |
Current CPC
Class: |
C03C
17/32 (20130101); C08G 18/62 (20130101); C09D
175/14 (20130101) |
Current International
Class: |
C03C
17/28 (20060101); C03C 17/32 (20060101); C08G
18/62 (20060101); C08G 18/00 (20060101); C09D
175/14 (20060101); B05D 003/02 () |
Field of
Search: |
;524/111,379,380,381,386,388,389,391,502,513,514
;427/385.5,388.1,389.7,391,393.5,395 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
R H. Grubbs in Comprehensive Organomet. Chem., Pergamon Press,
Ltd., New York, vol. 8, p. 499 ff. 1982. .
Angew. Chem. 107, p. 2179 ff (1995), in J. Am. Chem. Soc. 118, p.
100 ff (1996) and in J Chem. Soc., Chem. Commun. p. 1127 ff.
(1995)..
|
Primary Examiner: Woodward; Ana
Claims
We claim:
1. A coating composition comprising at least one polyol, wherein
the polyol is prepared by
subjecting an oligomer to hydroformylation to give an
aldehyde-functional product and
reducing the aldehyde-functional product to give the polyol,
wherein the oligomer is represented by the formula ##STR4##
wherein
R is selected from the group consisting of (CH.sub.2).sub.m,
##STR5##
and mixtures thereof,
n is an integer from 1 to 15,
m is an integer from 1 to 6,
X is methylene or an oxygen atom, and
R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are each independently
hydrogen or alkyl.
2. A coating composition according to claim 1, wherein m is 3.
3. A coating composition according to claim 1, wherein the polyol
has a hydroxyl number of from about 200 to about 650.
4. A coating composition according to claim 1, wherein the polyol
has a hydroxyl number of from about 250 to about 450.
5. A coating composition according to claim 1, comprising from 5 to
50% by weight of the polyol based on the total solids content of
the composition.
6. A coating composition according to claim 1, further comprising a
binder other than the polyol.
7. A coating composition according to claim 6, wherein the binder
other than the polyol is hydroxyl-functional.
8. A coating composition according to claim 6, wherein the binder
other than the polyol is selected from the group consisting of
polyacrylates, polyesters, polyurethanes, acrylicized
polyurethanes, acrylicized polyesters, polylactones,
polycarbonates, polyethers, acrylate diols, methacrylate diols, and
mixtures thereof.
9. A coating composition according to claim 1, wherein the
composition is curable at temperatures up to 180.degree. C.
10. A process for coating a substrate comprising applying to the
substrate a coating composition according to claim 1.
11. A process according to claim 10, wherein the substrate is
selected from the group consisting of metal, plastic, glass, wood,
paper, and combinations thereof.
12. A coating composition according to claim 1, wherein the polyol
is subjected to partial or complete hydrogenation.
13. A process for preparing a coating composition, comprising the
step of including in the composition at least one polyol at a level
of from 5 to 40 weight percent based on the total weight of the
solids of the coating composition, wherein the polyol is prepared
by
subjecting an oligomer to hydroformylation to give an
aldehyde-functional product and
reducing the aldehyde-functional product to give the polyol,
wherein the oligomer is represented by the formula ##STR6##
wherein
R is selected from the group consisting of (CH.sub.2).sub.m,
##STR7##
and mixtures thereof,
n is an integer from 1 to 15,
m is an integer from 1 to 6,
X is methylene or oxygen, and
R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are each independently
hydrogen or alkyl.
14. A process according to claim 13, wherein the coating
composition comprises from about 5 to about 20 weight percent of
the polyol based on the total weight of the solids of the coating
composition.
15. A process according to claim 13, further comprising the step of
including a binder other than the polyol in the composition.
16. A process according to claim 15, wherein the binder is
hydroxyl-functional.
17. A process according to claim 15, wherein the binder is selected
from the group consisting of polyacrylates, polyesters,
polyurethanes, acrylicized polyurethanes, acrylicized polyesters,
polylactones, polycarbonates, polyethers, acrylates diols,
methacrylate diols, and mixtures thereof.
18. A process according to claim 13, wherein the polyol is
subjected to partial or complete hydrogenation.
Description
FIELD OF THE INVENTION
The present invention relates to a coating composition, to a
process for preparing it and to its use.
BACKGROUND OF THE INVENTION
The coating materials that are known nowadays, examples being
clearcoats, topcoats and surfacers, are based on binders which are
required to have a large number of different functionalities in
order that required coating properties can be achieved. Such
coating systems are known, for example, from the German Patents DE
44 07 415, DE 44 07 409 or DE 43 10 414. The disadvantage of all
these coating materials is that the solids contents cannot be
increased ad infinitum. With these systems, therefore, reducing the
solvent emission is a possibility only within narrow confines.
SUMMARY OF THE INVENTION
The present invention, therefore, is based on the object of
providing a coating composition which relative to the coating
compositions known to date has an increased solids content in
conjunction with good scratch resistance and high reflow.
DETAILED DESCRIPTION OF THE INVENTION
This object is achieved in accordance with the invention in that
said composition comprises polyols I which are obtained by
subjecting oligomers of the formula I
in which R=--(--CH.sub.2 --).sub.m --, in which the index m is an
integer from 1 to 6, or ##STR2##
in which X=--CH.sub.2 -- or an oxygen atom
R.sup.1,R.sup.2,R.sup.3 and
R.sup.4 independently of one another=hydrogen atoms or alkyl;
and
the index n=an integer from 1 to 15;
to hydroformylation and reducing the resultant aldehyde-functional
products I to give the polyols I, which, if desired, are subjected
to partial or complete hydrogenation.
The value n in the formula I stands for the number of divalent
radicals R which have been introduced by ring-opening metathesis
reaction into the oligomers I derived from cyclic olefins such as,
for example, cyclopropene, cyclopentene, cyclobutene, cyclohexene,
cycloheptene, norbornene, 7-oxanorbornene or cyclooctene.
Preferably, as large as possible a proportion--such as, for
example, at least 40% by weight (as determined by integrating the
areas of the gas chromatograms; instrument: Hewlett Packard;
detector: flame ionization detector; column: DB 5.30 m.times.0.32
mm, covering: 1.mu.; temperature program: 60.degree. C. for 5
minutes, isothermal, heating rate 10.degree. C./min, max:
300.degree. C.)--of the oligomer mixtures I which can be employed
in accordance with the invention has a value of n>1. The value n
and thus the degree of ring-opening metathesis can, as set out
further below, be influenced by the activity of the metathesis
catalyst used.
The radicals R.sup.1,R.sup.2 R.sup.3 and R.sup.4 stand
independently of one another for hydrogen or alkyl, where the term
"alkyl" embraces straight-chain and branched alkyl groups.
Preferably, the groups concerned are straight-chain or branched
C.sub.1 -C.sub.15 -alkyl, preferably C.sub.1 -C.sub.10 -alkyl, and
with particular preference, C.sub.1 -C.sub.5 -alkyl groups.
Examples of alkyl groups are, in particular, methyl, ethyl, propyl,
1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl,
1,1-dimethylethyl, n-pentyl, 1-methylbutyl, 2-methylbutyl,
3-methylbutyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl,
2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl, 1-methylpentyl,
2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,2-dimethylbutyl,
1,3-dimethylbutyl, 2,3-dimethylbutyl, 1,1-dimethylpropyl,
1,2,2-trimethylpropyl, 1-ethylbutyl, 2-ethylbutyl,
1-ethyl-2-methylpropyl, n-heptyl, 1-methylhexyl, 1-ethylpentyl,
2-ethylpentyl, 1-propylbutyl, octyl, decyl, dodecyl, etc.
The degree of branching and the number of carbon atoms of the
terminal alkyl radicals R.sup.1,R.sup.2,R.sup.3 and R.sup.4 depend
on the structure of the acyclic monoolefins of the hydrocarbon
mixture used and on the activity of the catalyst. As described with
more precision below, the activity of the catalyst influences the
degree of cross-metathesis (self-metathesis) of the acyclic
olefins, with the formation of structurally new olefins into which,
formally, cyclopentene is then inserted in the manner of a
ring-opening metathesis addition polymerization.
Preference is given to the use of oligomer mixtures featuring an
increased proportion of oligomers having only one terminal double
bond. The oligomer is preferably prepared by subjecting a
hydrocarbon mixture obtained by cracking from petroleum processing
(C.sub.5 cut) and comprising a cyclic monoolefin such as
cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene,
cyclooctene, norbornene or 7-oxanorbornene, plus acyclic
monoolefins, to a homogeneous or heterogeneous metathesis
reaction.
The metathesis reaction formally comprises
a) the disproportionation of the acyclic monoolefins of the
hydrocarbon mixture by cross-metathesis,
b) the oligomerization of the cyclic monoolefin by ring-opening
metathesis,
c) chain termination by reaction of the oligomers from b) with an
acyclic olefin of the hydrocarbon mixture or of a product from
a),
it being possible for steps a) and/or b) and/or c) to be gone
through repeatedly, either alone or in combination.
Step a)
The cross-metathesis of the acyclic monoolefins will be illustrated
using the metathesis of 1-pentene and 2-pentene as an example:
CH.sub.2.dbd.CH--C.sub.3 H.sub.7 +.revreaction.propane+1
butene+2-hexane+3-hepteneCH.sub.3 --CH.dbd.CH--C.sub.2 H.sub.5
The combination of cross-metathesis of different acyclic olefins
and self-metathesis of the same acyclic olefins, such as, for
example, the self-metathesis of 1-pentene to ethene and 4-octene,
and repetition of this reaction, produce a large number of
monoolefins with different structures and numbers of carbon atoms,
these monoolefins forming the end groups of the oligomers I. The
proportion of cross-metathesis products, which increases as the
activity of the catalyst used goes up, also influences the double
bond content of the oligomers. For example, in the self-metathesis
of 1-pentene described above, ethene is released which, if desired,
can escape in gas form, with one double bond equivalent being
removed from the reaction. At the same time, there is an increase
in the proportion of oligomers without terminal double bonds. Thus
in the above example an oligomer without terminal double bonds is
formed, for example, by insertion of the cyclic monoolefin into
4-octene.
Step b) The average number of insertions of the cyclic monoolefin
in the growing chain in the sense of a ring-opening metathesis
addition polymerization determines the average molecular weight of
the oligomer mixture I that is formed. Preferably, oligomer
mixtures I having an average molecular weight of at least 274 g per
mol are formed by the process of the invention, which corresponds
to an average number of three units of a cyclic monoolefin per
oligomer.
Step c)
Chain termination takes place by reaction of oligomers that still
have an active chain end in the form of a catalyst complex
(alkylidene complex) with an acyclic olefin; in the course of this
reaction, ideally, an active catalyst complex is recovered. In that
case, the acyclic olefin may originate unchanged from the
hydrocarbon mixture originally employed for the reaction, or may
have been modified in a cross-metathesis in accordance with stage
a).
Very generally, the process is suitable for preparing oligomers I
from hydrocarbon mixtures which comprise acyclic and cyclic
monoolefins: monoolefins such as, for example, cyclobutene,
cyclopentene, cyclohexene, cycloheptene, norbornene or
7-oxanorbornene, especially cyclopentene. Variants of this process
are described, for example, in the article by M. Schuster and S.
Bleckert in Angewandte Chemie, 1997, Volume 109, pages 2124 to
2144.
Preference is given to the use of a hydrocarbon mixture obtained
industrially in the processing of petroleum, it being possible if
desired to subject said mixture to catalytic partial hydrogenation
beforehand in order to remove dienes. A particularly suitable
mixture for use in the present process is, for example, a mixture
enriched in saturated and unsaturated C.sub.5 -hydrocarbons
(C.sub.5 cut). In order to obtain the C.sub.5 cut it is possible,
for example, first to subject pyrolysis benzine obtained in the
steam cracking of naphtha to a selective hydrogenation in order to
convert, selectively, the dienes and acetylenes present into the
corresponding alkanes and alkenes, and subsequently to subject the
product to a fractional distillation, producing firstly the C.sub.6
-C.sub.8 cut, which is important for further chemical syntheses and
comprises the aromatic hydrocarbons, and secondly the C.sub.5 cut,
which is used for the process of the invention.
The C.sub.5 cut generally has an overall olefin content of at least
30% by weight, preferably at least 40% by weight and, in
particular, at least 50% by weight.
Suitable in this context are C.sub.5 hydrocarbon mixtures having an
overall cyclopentene content of at least 5% by weight, preferably
at least 10% by weight and, in particular, at least 12% by weight,
and generally not more than 30% by weight, preferably not more than
20% by weight.
Furthermore, suitable C.sub.5 hydrocarbon mixtures have a
proportion of pentene isomers among the acyclic monoolefins of at
least 70% by weight, preferably at least 80% by weight and, in
particular, at least 90% by weight.
The preparation process can also be performed with a C.sub.5 cut
which is obtained industrially and has an overall olefin content
of, for example, from 50 to 60% by weight, such as about 56%, a
cyclopentene content of, for example, from 10 to 20% by weight,
such as about 15% by weight, and a content of pentene isomers of,
for example, 33 to 43% by weight, such as about 38% by weight, with
about 16% by weight being accounted for by the n-pentene and about
22% by weight by isomeric pentenes.
In one specific embodiment, the hydrocarbon mixture used in the
preparation process comprises the C.sub.5 cut and a petroleum
fraction (raffinate 2) which comprises acyclic C.sub.4 olefins.
In another specific embodiment of the preparation process a
hydrocarbon mixture is used which comprises the C.sub.5 cut and
ethene. In this case, oligomer mixtures I having an increased
double bond content are obtained. This is achieved first by
ethenolysis of the acyclic n- and iso-pentenes present in the
C.sub.5 cut to give shorter-chain .alpha.-olefins, such as propene
and 1-butene, which react with cyclopentene in a ring-opening
metathesis reaction to form oligomers I having in each case one
terminal double bond. In addition, in the presence of ethene, the
self-metathesis of the acyclic olefins to form further ethene,
such, for example, as the self-metathesis of 1-pentene to form
ethene and 4-octene, which as a chain terminating reagent leads to
products without terminal double bonds, is suppressed. Second, a
further increase in the double bond content is achieved through the
ethenolysis of cyclopentene with ethene to give 1,6-heptadiene.
This results in sequences of oligomers each of which have two
terminal double bonds. When oligomer mixtures I obtained in this
way, having an increased double bond content, are used for the
functionalization, the result is preferably oligomer mixtures I
having an increased density of functionalities.
Suitable catalysts for the metathesis are known from the prior art
and include homogeneous and heterogeneous catalyst systems. In
general, the catalysts suitable for the preparation process are
based on a transition metal from subgroup 6, 7 or 8 of the Periodic
Table, with preference being given to the use of catalysts based on
Mo, W, Re and Ru.
Suitable homogeneous catalyst systems are generally transition
metal compounds which, alone or in combination with a cocatalyst
and/or in the presence or absence of the olefin precursors, are
capable of forming a catalytically active metal carbene complex.
Such systems are described, for example, by R. H. Grubbs in
Comprehensive Organomet. Chem., Pergamon Press, Ltd., New York,
Vol. 8, p. 499 ff. (1982).
Suitable catalyst/cocatalyst systems based on W, Mo and Re may
comprise, for example, at least one soluble transition metal
compound and an alkylating agent. Examples include MOCl.sub.2
(NO).sub.2 (PR.sub.3).sub.2 /Al.sub.2 (CH.sub.3).sub.3 Cl.sub.3 ;
WCl.sub.6 /BuLi; WCl.sub.6 /EtAlCl.sub.2 (Sn(CH.sub.3).sub.4 /EtOH;
WOCl.sub.4 /Sn(CH.sub.3).sub.4 ; WOCl.sub.2 (O-[2,6-Br.sub.2
--C.sub.6 H.sub.3 ])/Sn(CH.sub.3).sub.4 ; CH.sub.3 ReO.sub.3
/C.sub.2 H.sub.5 AlCl.sub.2, the four latter systems being
preferred for the process of the invention.
Further transition metal/alkylidene complexes suitable as
metathesis catalysts are described by R. R. Schrock in Acc. Chem.
Res., 23, p. 158 ff (1990). In general terms these are
tetracoordinated Mo- and W-alkylidene complexes, which in addition
have two bulky alkoxy ligands and one imido ligand. Of these,
preference is given for the process of the invention to the use of
((CH.sub.3).sub.3 CO).sub.2 Mo(.dbd.N-[2,6-(i-C.sub.3
H.sub.7).sub.2 --C.sub.6 H.sub.3 ])(.dbd.CHC(CH.sub.3).sub.2
C.sub.6 H.sub.5) and [(CF.sub.3).sub.2 C(CH.sub.3)O].sub.2
Mo(.dbd.N-[2,5-(i-C.sub.3 H.sub.7)--C.sub.6 H.sub.3
])(.dbd.CH(CH.sub.3).sub.2 C.sub.6 H.sub.5).
In particular, the catalysts used as homogeneous metathesis
catalysts are those which are described in Angew. Chem. 107, p.
2179 ff. (1995), in J. Am. Chem. Soc. 118, p. 100 ff. (1996) and in
J. Chem. Soc., Chem. Commun, p. 1127 ff. (1995). These include, in
particular, RuCl.sub.2 (.dbd.CHR)(PR'.sub.3).sub.2, preferably
RUCl.sub.2 (.dbd.CHC.sub.6 H.sub.5)(P(C.sub.6
H.sub.11).sub.3).sub.2, (.eta..sup.6 -p-cymene)RuCl.sub.2
(p(C.sub.6 H.sub.11).sub.3) and 3 mole equivalents of diazoalkane
((CH.sub.3).sub.3 SiCHN.sub.2 or C.sub.6 H.sub.5 CHN.sub.2)
generated in situ.
Suitable heterogeneous catalyst systems comprise, in general, a
transition metal compound on an inert support, said system being
capable without a cocatalyst of forming a catalytically active
alkylidene complex by reaction with the olefin precursors. It is
preferred to use Re.sub.2 O.sub.7 and CH.sub.3 ReO.sub.3.
Suitable inorganic supports are the oxides customary for this
purpose, especially silicon oxides and aluminum oxides,
aluminosilicates, zeolites, carbides, nitrides, etc., and mixtures
of them. Preferred for use as supports are Al.sub.2 O.sub.3,
SiO.sub.2 and mixtures of them, alone or in combination with
B.sub.2 O.sub.3 and Fe.sub.2 O.sub.3.
The abovementioned homogeneous and heterogeneous catalyst systems
differ greatly in their catalytic activity, so that the individual
catalysts have different optimum reaction conditions for the
metathesis. As already described above, the catalytic activity with
respect to the cross-metathesis (step a)) also influences the
product distribution of the oligomer mixtures I derived from
cyclopentene. For instance, the ruthenium-based homogeneous
catalyst systems RuCl.sub.2 (.dbd.CHC.sub.6 H.sub.5)(P(C.sub.6
H.sub.11).sub.3).sub.3, (.eta..sup.6 -p-cymene)-RuCl.sub.2
(P(C.sub.6 H.sub.11).sub.3)/(CH.sub.3).sub.3 SICHN.sub.2 and
(.eta..sup.6 -p-cymene)-RuCl.sub.2 (P(C.sub.6 H.sub.11)
.sub.3)/C.sub.6 H.sub.5 CHN.sub.2 are particularly suitable for the
preparation process. Of these compounds, the first ruthenium
complex has a higher catalytic activity than the last two, and so
under otherwise identical reaction conditions leads to higher
space-time yields. At the same time, however, in the case of the
first complex there is also an increased level of cross-metathesis,
which is also accompanied in part by the release of ethene;
therefore, the resultant cyclopentene-derivative oligomer mixture I
has a somewhat smaller proportion of double bonds, which is
manifested, for example, in a lower iodine number. Moreover,
because of the cross-metathesis, a larger number of acylic olefins
without terminal double bonds is available, so that the first
homogeneous ruthenium catalyst produces a higher proportion of
cyclopentene-derived oligomers I having only one terminal double
bond or none. The two latter ruthenium complexes have a somewhat
lower catalytic activity than the first, so that when they are used
the cyclopentene-derived oligomer mixtures I obtained in accordance
with the process of the invention have a higher double bond content
and thus a higher iodine number and also a larger proportion of
terminal double bonds.
The heterogeneous catalyst systems also have the above-described
differences in activity, with the corresponding influence on the
metathesis products. If CH.sub.3 ReO.sub.3 on Al.sub.2 O.sub.3 is
used as a heterogeneous catalyst for the preparation process, it
has a higher catalytic activity than the corresponding homogeneous
catalyst system comprising CH.sub.3 ReO.sub.3 /(C.sub.2
H.sub.5)AlCl.sub.2.
As a homogeneous catalyst it is advantageous to use Re.sub.2
O.sub.7 on Al.sub.2 O.sub.3. This has an activity comparable
approximately with that of RuCl.sub.2 (.dbd.CHC.sub.6
H.sub.5)(P(C.sub.6 H.sub.11).sub.3).sub.2 and a similar product
distribution and, following regeneration in a stream of air at
elevated temperatures, such as about 550.degree. C., can be used
again.
If desired, therefore, it is possible depending on the catalyst
used to obtain cyclopentene-derived oligomer mixtures I having
varying double bond contents and varying proportions of terminal
double bonds.
In one specific embodiment of the preparation process the
metathesis catalyst used is a homogeneous ruthenium-based catalyst
selected from RuCl.sub.2 (.dbd.CHC.sub.6 H.sub.5)(P(C.sub.6
H.sub.11).sub.3).sub.2, (.eta..sup.6 -p-cymene)RuCl.sub.2
(P(C.sub.6 H.sub.11).sub.3)/(CH.sub.3).sub.3 SiCHN.sub.2 and
(.eta..sup.6 -p-cymene)RuCl.sub.2 (P(C.sub.6
H.sub.11).sub.3)/C.sub.6 H.sub.5 CHN.sub.2 which is added to the
reaction mixture as a solution in an organic solvent. Examples of
suitable solvents are aromatic hydrocarbons, such as toluene and
xylene, and halogenated alkanes, such as CH.sub.2 Cl.sub.2,
CHCl.sub.3 etc.
The reaction temperature with reactive catalyst systems is from -20
to 200.degree. C., preferably from 0 to 100.degree. C. and, in
particular, from 20 to 80.degree. C.
The reaction can be conducted at a superatmospheric pressure of up
to 5 bar, preferably up to 2 bar, or, with particular preference,
can be carried out at ambient pressure.
In a further specific embodiment of the preparation process the
metathesis catalyst used is a heterogeneous rhenium-based catalyst
selected from CH.sub.3 ReO.sub.3 /Al.sub.2 O.sub.3 and, preferably,
Re.sub.2 O.sub.7 /Al.sub.2 O.sub.3, which is added to the reaction
mixture without the addition of solvent.
In the case of these catalysts, which are somewhat less active than
the abovementioned homogeneous catalyst systems, the reaction
temperature is from about 20 to 120.degree. C., in particular from
40 to 80.degree. C.
The reaction is preferably conducted at a superatmospheric pressure
of from 2 to 20 bar, preferably from 3 to 15 bar and, in
particular, from 4 to 12 bar.
In terms of process regime, the preparation process can be
performed either continuously or batchwise. Suitable reaction
apparatuses are known to the person skilled in the art and are
described, for example, in Ullmanns Enzyklopadie der technischen
Chemie, Vol. 1, p. 743 ff. (1951). It includes for the batchwise
process, for example, stirred vessels and for the continuous
process, for example, tube reactors.
In one suitable batchwise variant of the preparation process it is
possible to react, for example, the C.sub.5 cut over one of the
homogeneous ruthenium catalysts described above as being preferred,
which is produced if desired in situ within the reactor vessel, in
a metathesis reaction to give the cyclopentene-derived oligomer
mixtures I.
In a further suitable, continuous variant of the preparation
process it is possible to react, for example, the C.sub.5 cut over
one of the heterogeneous rhenium catalysts described above as being
preferred, in a tube reactor.
Both possible process variants give space-time yields, depending on
the catalyst used and on the other reaction parameters, especially
the reaction temperature, of at least 10 g l.sup.-1 h.sup.-1,
preferably at least 15 g l.sup.-1 h.sup.-1. Depending on the
activity of the catalyst, however, it is also possible to obtain
substantially higher space-time yields of up to about 500 g
l.sup.-1 h.sup.-1.
The reaction mixture is separated by customary methods. These
include, for example, fractional distillation, at atmospheric or
reduced pressure, or separation at elevated temperatures and
atmospheric pressure in a falling-film evaporator. Low-boiling
fractions comprising still unreacted olefins can if desired be
recycled to the reaction apparatus. Advantageously, extensive
reaction of the olefins present in the C.sub.5 cut to oligomers I
is achieved in the course of the preparation process, so that the
low boilers which are separated off comprise a C.sub.5 hydrocarbon
mixture with predominantly saturated cyclic and acyclic
compounds.
As described above, the number and position of the double bonds in
the oligomers I can be influenced by the reaction conditions,
especially the particular catalyst used. The process described
produces cyclopentene oligomers I for which the iodine number is at
least 250 g of I.sub.2 /100 g oligomers I, preferably at least 300
g of I.sub.2 /100 g of oligomers I.
The average molecular weight of these oligomers I derived from
cyclic monoolefins, especially cyclopentene, is at least 274 g/mol,
which corresponds to an average conversion of three cyclopentene
units per oligomer, with chain termination by an acyclic pentene
(and not by a cross-metathesis product) being assumed in this
case.
In order to prepare the polyols I for use in accordance with the
invention, the oligomers I detailed above are subjected to
customary and conventional hydroformylation. Here, in general, the
oligomers I are reacted with hydrogen and carbon monoxide in the
presence of catalysts comprising suitable transition metals under
atmospheric pressure or under superatmospheric pressure at
temperatures from 50 to 150.degree. C. to give aldehyde-functional
products I.
An example of a suitable transition metal is rhodium.
The resultant products I are isolated and are reduced in a
customary and conventional manner to give the polyols I to be used
in accordance with the invention. Reducing agents suitable for this
purpose are all those with which aldehyde groups can be reduced to
hydroxyl groups. Examples of suitable reducing agents are
borohydrides, such as sodium tetrahydroboronate, or hydrogen in the
presence of hydrogenation catalysts.
Examples of suitable hydroformylation and reduction processes are
described in European Patent 0 502 839.
The polyols I to be used in accordance with the invention can be
subjected in a customary and conventional manner to partial or
complete hydrogenation. Suitable reducing agents for this purpose
include those mentioned above.
The polyols I to be used in accordance with the invention have a
hydroxyl number (OHN) of from 200 to 650, in particular 250 to 450.
Their number-average molecular weight M.sub.n, determined with the
aid of gel permeation chromatography using polystyrene as the
internal standard, lies within the range from 400 to 1000, in
particular from 400 to 600. Their mass-average molecular weight
M.sub.w, determined with the aid of gel permeation chromatography
and polystyrene as the internal standard, lies within the range
from 600 to 2000, in particular from 600 to 1100. The
polydispersity M.sub.n /M.sub.w is from 1.4 to 3, in particular
from 1.7 to 1.9.
An example of a particularly advantageous polyol to be used in
accordance with the invention has an OHN of 350, an M.sub.n of 561
and an M.sub.w of 1,068.
The polyols I to be used in accordance with the invention are
present in the coating compositions of the invention in an amount
of from 5 to 50% by weight, based on the solids content of the
coating composition. Particularly advantageous coating compositions
of the invention are obtained by substituting up to 40%, preferably
up to 30%, with particular preference up to 20% and, in particular,
up to 10% by weight of the solids of a coating composition by at
least one polyol I to be used in accordance with the invention.
Suitable candidates for the hydroxy-functional binder or for the
mixture of hydroxy-functional binders are preferably binders based
on polyacrylates, polyesters, polyurethanes, acrylicized
polyurethanes, acrylicized polyesters, polylactones,
polycarbonates, polyethers and/or (meth)acrylatediols.
Hydroxy-functional binders are known to the person skilled in the
art, and many suitable examples are available on the market.
Preference is given to the use of polyacrylates, polyesters and/or
polyurethanes, especially polyacrylates and/or polyesters.
Polyacrylate resins have OHNs of from 40 to 240, preferably from 60
to 210 and, with very particular preference, from 100 to 200, acid
numbers of from 0 to 35, preferably from 0 to 23 and, with very
particular preference, from 3.9 to 15.5, glass transition
temperatures of from -35 to +70.degree. C., preferably from -20 to
+40.degree. C. and, with very particular preference, from -10 to
+15.degree. C., and number-average molecular weights of from 1500
to 30,000, preferably from 1500 to 15,000 and, with very particular
preference, from 1500 to 5000.
The glass transition temperature of the polyacrylate resins is
determined by the nature and amount of the monomers employed. The
monomers can be selected by the person skilled in the art with the
aid of the following formula, which can be used to calculate
approximately the glass transition temperatures of polyacrylate
resins:
Tg=glass transition temperature of the polyacrylate resin
W.sub.n =proportion by weight of the nth monomer
Tg.sub.n =glass transition temperature of the homopolymer of the
nth monomer
x=number of different monomers
Measures to control the molecular weight (for example, the
selection of appropriate polymerization initiators, use of chain
transfer agents, etc.) are part of the knowledge of the person
skilled in the art and need not be elucidated further here.
As the hydroxy-functional binder component it is also possible, for
example, to employ polyacrylate resins which can be prepared by
subjecting (a2) from 10 to 92, preferably from 20 to 60% by weight
of an alkyl or cycloalkyl acrylate or of an alkyl or cycloalkyl
methacrylate having 1 to 18, preferably 4 to 13 carbon atoms in the
alkyl or cycloalkyl radical, or mixtures of such monomers, (b2)
from 8 to 60, preferably from 12.5 to 38.5% by weight of a
hydroxyalkyl acrylate or of a hydroxyalkyl methacrylate having 2 to
4 carbon atoms in the hydroxyalkyl radical, or mixtures of such
monomers, (c2) from 0.0 to 5.0, preferably from 0.7 to 3.0% by
weight of acrylic acid or methacrylic acid, or mixtures of these
monomers, and (d2) from 0 to 50, preferably from 0 to 30% by weight
of ethylenically unsaturated monomers which are different from but
copolymerizable with (a2), (b2) and (c2), or mixtures of such
monomers, to addition polymerization to give polyacrylate resins
having hydroxyl numbers of from 40 to 240, preferably from 60 to
150, acid numbers of from 0 to 35, preferably from 5 to 20, glass
transition temperatures of from -35 to +70 degrees C., preferably
from -20 to +40 degrees C., and number-average molecular weights of
from 1500 to 30,000, preferably from 1500 to 15,000 (determined by
gel permeation chromatography, with polystyrene as standard).
Examples of components (a2) are methyl, ethyl, propyl, n-butyl,
isobutyl, tert-butyl, pentyl, hexyl, heptyl and 2-ethylhexyl
acrylate and methacrylate, and also cyclohexyl acrylate and
cyclohexyl methacrylate. Examples of components (b2) are
hydroxyethyl, hydroxypropyl and hydroxybutyl acrylate or
methacrylate. Examples of components (d2) are vinylaromatic
compounds, such as styrene, vinyltoluene, alpha-methylstyrene,
alpha-ethylstyrene, ring-substituted diethylstyrenes,
isopropylstyrene, butylstyrenes and methoxystyrenes; vinyl ethers,
such as ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl
ether, n-butyl vinyl ether and isobutyl vinyl ether, and vinyl
esters, such as vinyl acetate, vinyl propionate, vinyl butyrate,
vinyl pivalate and the vinyl ester of 2-methyl-2-ethylheptanoic
acid. The hydroxyl number and the acid number of the polyacrylate
resins can easily be controlled by the person skilled in the art by
way of the amount of component (b2) and/or (c2) employed.
Further suitable polyacrylate components are the hydroxy-functional
compounds mentioned in European Patent Application EP 0 767 185 and
in the U.S. Pat. Nos. 5,480,943, 5,475,073 and 5,534,598.
As the hydroxy-functional binder component, use is also made, for
example, of polyacrylate resins obtainable by subjecting (A1) from
10 to 51% by weight, preferably from 25 to 41% by weight, of
4-hydroxy-n-butyl acrylate or 4-hydroxy-n-butyl methacrylate, or a
mixture of 4-hydroxy-n-butyl acrylate and 4-hydroxy-n-butyl
methacrylate, preferably 4-hydroxy-n-butyl acrylate, (A2) from 0 to
36% by weight, preferably from 0.1 to 20% by weight, of a
hydroxyl-containing ester of acrylic acid or of a
hydroxyl-containing ester of methacrylic acid which is different
from (A1), or a mixture of such monomers, (A3) from 28 to 85% by
weight, preferably from 40 to 70% by weight, of an aliphatic or
cycloaliphatic ester of methacrylic acid having at least 4 carbon
atoms in the alcohol residue, this monomer being different from
(A1) and (A2), or a mixture of such monomers, (A4) from 0 to 3% by
weight, preferably from 0.1 to 2% by weight, of an ethylenically
unsaturated carboxylic acid or of a mixture of ethylenically
unsaturated carboxylic acids, and (A5) from 0 to 20% by weight,
preferably from 5 to 15% by weight, of an unsaturated monomer which
is different from (A1), (A2), (A34) and (A4), or a mixture of such
monomers, to addition polymerization to give a polyacrylate resin
having a hydroxyl number of from 60 to 200, preferably from 100 to
160, an acid number of from 0 to 35, preferably from 0 to 25, and a
number-average molecular weight of from 1500 to 10,000, preferably
from 2500 to 5000, the sum of the parts by weight of components
(A1) to (A5) always being 100% and the composition of component
(A3) being chosen such that addition polymerization of component
(A3) alone gives a polymethacrylate resin having a glass transition
temperature of from +10 to +100 degrees C., preferably from +20 to
+60 degrees C. Examples of component (A2) are hydroxyalkyl esters
of acrylic acid, such as hydroxyethyl acrylate and hydroxypropyl
acrylate, and hydroxyalkyl esters of methacrylic acid, such as
hydroxyethyl methacrylate and hydroxypropyl methacrylate, the
choice being made such that addition polymerization of component
(A2) alone gives a polyacrylate resin having a glass transition
temperature of 0 to +80 degrees C., preferably from +20 to +60
degrees C. Examples of component (A3) are aliphatic esters of
methacrylic acid having 4 to 20 carbon atoms in the alcohol
residue, such as n-butyl, isobutyl, tert-butyl, 2-ethylhexyl,
stearyl and lauryl methacrylate, and cycloaliphatic esters of
methacrylic acid, such as cyclohexyl methacrylate. As component
(A4) it is preferred to employ acrylic and/or methacrylic acid.
Examples of component (A5) are vinylaromatic hydrocarbons, examples
being styrene, .alpha.-alkylstyrene and vinyltoluene, amides of
acrylic and methacrylic acid, examples being methacrylamide and
acrylamide, nitrites of acrylic and methacrylic acid, vinyl ethers
and vinyl esters. As component (A5) it is preferred to employ
vinylaromatic hydrocarbons, especially styrene. The composition of
component (A5) is preferably made such that addition polymerization
of component (A5) alone gives a polymer having a glass transition
temperature of from +70 to +120 degrees C., preferably from +80 to
+100 degrees C. These polyacrylate resins can be prepared by
well-known techniques of addition polymerization (see e.g.
Houben-Weyl, Methoden der organischen Chemie, 4th edition, volume
14/1, pages 24 to 255 (1961)). They are preferably prepared by
means of solution polymerization. In this case, customarily, an
organic solvent or solvent mixture is introduced as the initial
charge and is heated to boiling. The monomer mixture to be
polymerized, and also one or more polymerization initiators, are
then added continuously to this organic solvent or solvent mixture.
The addition polymerization takes place at temperatures between 100
and 200.degree. C., preferably between 130 and 180.degree. C.
Polymerization initiators employed are preferably initiators which
form free radicals. The nature and amount of the initiators are
commonly chosen such that the supply of free radicals available
during the feed phase at the polymerization temperature is as
constant as possible.
Examples of initiators which can be employed are dialkyl peroxides,
such as di-tert-butyl peroxide and dicumyl peroxide,
hydroperoxides, such as cumene hydroperoxide and tert-butyl
hydroperoxide, peresters, such as tert-butyl perbenzoate,
tert-butyl perpivalate, tert-butyl per-3,5,5-trimethylhexanoate and
tert-butyl per-2-ethylhexanoate, or bisazo compounds, such as
azobisisobutyronitrile. The polymerization conditions (reaction
temperature, feed time of the monomer mixture, nature and amount of
the organic solvents and polymerization initiators, possible use of
molecular weight regulators, e.g., mercaptans, thioglycolic esters
and chlorinated hydrocarbons) are selected such that the
polyacrylate resins have a number-average molecular weight like
that indicated (determined by gel permeation chromatography using
polystyrene as calibration substance). The acid number can be
adjusted by the person skilled in the art using appropriate amounts
of component (A4). Similar comments apply to the adjustment of the
hydroxyl number, which can be controlled by way of the amount of
component (A1) and (A2) employed.
The preparation of these addition polymers is described, for
example, in the international patent application WO 97/17431.
It is additionally possible to use products available on the market
which are sold under the brand name Joncryl.RTM., an example being
Joncryl.RTM. SCX 922.
It is possible to employ suitable polyester resins and alkyd
resins, and they can be prepared by reacting (a1) a cycloaliphatic
or aliphatic polycarboxylic acid or a mixture of such
polycarboxylic acids, (b1) an aliphatic or cycloaliphatic polyol
having more than two hydroxyl groups in the molecule, or a mixture
of such polyols, (c1) an aliphatic or cycloaliphatic diol or a
mixture of such diols, and (d1) an aliphatic linear or branched
saturated monocarboxylic acid or a mixture of such monocarboxylic
acids, in a molar ratio of
(a1):(b1):(c1):(d1)=1.0:0.2-1.3:0.0-1.1:0.0-1.4, preferably
1.0:0.5-1.2:0.0-0.6:0.2-0.9, to give a polyester resin or alkyd
resin. Examples of constituent (a1) are hexahydrophthalic acid,
1,4-cyclohexanedicarboxylic acid, endomethylenetetrahydrophthalic
acid, oxalic acid, malonic acid, succinic acid, glutaric acid,
adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic
acid. Examples of constituent (b1) are pentaerythritol,
trimethylolpropane, trimethylolethane and glycerol. Examples of
constituent (c1) are ethylene glycol, diethylene glycol, propylene
glycol, neopentyl glycol, 2-methyl-2-propyl-1,3-propanediol,
2-ethyl-2-butyl-1,3-propanediol, 2,2,4-trimethyl-1,5-pentanediol,
2,2,5-trimethyl-1,6-hexanediol, neopentyl glycol hydroxypivalate,
and dimethylolcyclohexane. Examples of constituent (d1) are
2-ethylhexanoic acid, lauric acid, isooctanic acid, isononanic
acid, and monocarboxylic acid mixtures obtained from coconut oil or
palm kernel oil.
The preparation of hydroxyl-bearing polyester resins and/or alkyd
resins is described, for example, in Ullmanns Encyklopadie der
technischen Chemie, third edition, Vol. 14, Urban &
Schwarzenberg, Munich, Berlin 1963, pages 80 to 89 and pages 99 to
105, and in the following books: Resines Alkydes-Polyesters by J.
Bourry, Paris, Dunod 1952, Alkyd Resins by C. R. Martens, Reinhold
Publishing Corporation, New York 1961, and Alkyd Resin Technology
by T. C. Patton, Interscience Publishers 1962.
Also suitable, furthermore, are polyurethane-based binders.
Urethane (meth)acrylates are well known to the person skilled in
the art and therefore need not be elucidated further. Examples of
suitable polyurethane resins are the resins described in the
following German, European and international patents: DE 44 01 544,
DE 195 34 316, EP 0 708 788 and WO 97/14731.
By the partial replacement of the binders or binder mixtures
described with the polyols I to be used in accordance with the
invention, it is possible surprisingly to achieve relatively high
solids contents without the occurrence of substantial disadvantages
as far as the profiles of properties of the coatings are concerned.
For instance, it has been possible, with markedly higher solids
contents of the coating compositions of the invention, to achieve
scratch-resistance and film-hardness values that are just as good,
with comparable acid resistance of the coatings, which in
accordance with the prior art to date was possible only by
observing lower solids contents. In accordance with the invention,
therefore, it is possible in particular to achieve a higher reflow
potential and, owing to the higher solids content, a reduction in
solvent emission.
In addition to the binders described, the coating compositions of
the invention also comprise other constituents which are customary
according to the prior art. In this context it is possible to
design the coating compositions of the invention as one-component
or else multicomponent systems. Such systems differ essentially in
the nature of the crosslinking agent that is employed. In both
cases, suitable crosslinking agents are all those which react with
hydroxyl groups under the curing conditions. Examples of suitable
crosslinking agents are amino resins, siloxane-functional compounds
or resins, anhydride-functional compounds or resins, blocked and
nonblocked polyisocyanates and/or alkoxycarbonylaminotriazines, but
especially blocked polyisocyanates and/or
tris(alkoxycarbonylamino)triazines.
Both in one-component and in two-component or multicomponent
systems it is possible in accordance with the invention to employ
blocked isocyanates or a mixture of blocked polyisocyanates.
The blocked isocyanates which can be employed are preferably of
such a configuration that they comprise both isocyanates blocked
with a blocking agent (Z1) and isocyanate groups blocked with a
blocking agent (Z2), the blocking agent (Z1) being a
dialkylmalonate or a mixture of dialkyl malonates, the blocking
agent (Z2) being different from (Z1) and being a blocking agent
comprising active methylene groups, an oxime, or a mixture of these
blocking agents, and the ratio of equivalents between the
isocyanate groups blocked with (Z1) and the isocyanate groups
blocked with (Z2) being between 1.0:1.0 and 9.0:1.0, preferably
between 8.0:2.0 and 6.0:4.0 and with particular preference, between
7.5:2.5 and 6.5:3.5.
However, it is also possible to use dimethylpyrazole and/or
substituted triazoles as blocking agents.
The blocked isocyanate is preferably prepared as follows:
A polyisocyanate or a mixture of polyisocyanates is reacted
conventionally with a mixture of the blocking agents (Z1) and (Z2),
the mixture of the blocking agents (Z1) and (Z2) comprising the
blocking agents (Z1) and (Z2) in a molar ratio which lies between
1.0:1.0 and 9.0:1.0, preferably between 8.0:2.0 and 6.0:4.0 and,
with particular preference, between 7.5:2.5 and 6.5:3.5.
The polyisocyanate or the mixture of polyisocyanates can be reacted
with the mixture of the blocking agents (Z1) and (Z2) to such an
extent that isocyanate groups can no longer be detected. In
practice, this may require the use of very large excesses of
blocking agents and/or very long reaction times.
It has been found that, even then, coating materials having good
properties are obtained when at least 50, preferably at least 70,
percent of the isocyanate groups of the polyisocyanate or of the
mixture of polyisocyanates are reacted with the mixture of the
blocking agents (Z1) and (Z2) and the remaining isocyanate groups
are reacted with a hydroxyl-containing compound or with a mixture
of hydroxyl-containing compounds. Hydroxyl-containing compounds
employed are preferably low molecular mass aliphatic or
cycloaliphatic polyols, such as neopentyl glycol,
dimethylolcyclohexane, ethylene glycol, diethylene glycol,
propylene glycol, 2-methyl-2-propyl-1,3-propanediol,
2-ethyl-2-butyl-1,3-propanediol, 2,2,4-trimethyl-1,5-pentanediol
and 2,2,5-trimethyl-1,6-hexanediol, or the hydroxyl-containing
binder which can be employed as constituent (1).
A suitable blocked polyisocyanate is also obtainable by mixing
blocked polyisocyanates with the blocking agent (Z1) and/or (Z2) in
a proportion such as to give a mixture in which the ratio of
equivalents between the isocyanate groups blocked with (Z1) and the
isocyanate groups blocked with (Z2) lies between 1.0:1.0 and
9.0:1.0, preferably between 8.0:2.0 and 6.0:4.0, and with
particular preference, between 7.5:2.5 and 6.5:3.5.
In principle, all polyisocyanates that can be employed in the
coatings field can be used to prepare the blocked polyisocyanate.
It is preferred, however, to employ polyisocyanates whose
isocyanate groups are attached to aliphatic or cycloaliphatic
radicals. Examples of such polyisocyanates are hexamethylene
diisocyanate, isophorone diisocyanate, trimethylhexamethylene
diisocyanate, dicyclohexylmethane diisocyanate and
1,3-bis(2-isocyanatopropyl-2-yl)benzene (TMXDI), and also adducts
of these polyisocyanates with polyols, especially low molecular
mass polyols, such as trimethylolpropane, and isocyanurate- and
biuret-functional polyisocyanates derived from these
polyisocyanates. Also suitable are 1,3- and/or
1,4-bis(isocyanatomethyl)cycloalkanes, such as 1,3- and/or
1,4-bis(isocyanatomethyl)cyclohexane.
As polyisocyanates it is particularly preferred to employ
hexamethylene diisocyanate and isophorone diisocyanate,
isocyanurate- or biuret-functional polyisocyanates that are derived
from said diisocyanates and include preferably more than two
isocyanate groups in the molecule, and also reaction products of
hexamethylene diisocyanate and isophorone diisocyanate or of a
mixture of hexamethylene diisocyanate and isophorone diisocyanate
with 0.3-0.5 equivalents of a low molecular mass polyol having a
molecular weight from 62 to 500, preferably from 104 to 204, in
particular a triol, such as trimethylolpropane, for example.
Blocking agents (Z1) employed are dialkyl malonates or a mixture of
dialkyl malonates. Examples of dialkyl malonates that can be
employed are those having 1 to 6 carbon atoms in each of the alkyl
radicals, examples being dimethyl malonate and diethyl malonate,
the latter being employed with preference. Blocking agents (Z2)
employed are different from (Z1) and are blocking agents containing
active methylene groups, and oximes, and also mixtures of these
blocking agents. Examples of blocking agents which can be employed
as blocking agents (Z2) are methyl, ethyl, propyl, butyl, pentyl,
hexyl, heptyl, octyl, nonyl, decyl or dodecyl acetoacetate, acetone
oxime, methyl ethyl ketoxime, acetylacetone, formaldoxime,
acetaldoxime, benzophenoxime, acetoxime and diisobutyl ketoxime. As
blocking agent (Z2) it is preferred to employ an alkyl acetoacetate
having 1 to 6 carbon atoms in the alkyl radical, or a mixture of
such alkyl acetoacetates, or a ketoxime or a mixture of ketoximes.
Particular preference is given to the use of ethyl acetoacetate or
methyl ethyl ketoxime as the blocking agent (Z2).
As crosslinking agents, it is also possible to employ
tris(alkoxycarbonylamino)triazines of the formula ##STR3##
where R is methyl and/or other alkyl groups, especially butyl
groups. It is also possible to employ derivatives of said
compounds. For the constituent (2) it is preferred to employ
tris(alkoxycarbonylamino)triazines as are described in U.S. Pat.
No. 5,084,541.
The coating compositions of the invention can also be
multicomponent systems, preferably two-component systems. In this
case the coating composition has a second component which as a
crosslinking agent comprises at least one nonblocked di- and/or
polyisocyanate which may or may not be dissolved in one or more
organic solvents. In addition, however, blocked polyisocyanate or a
mixture of blocked isocyanates can also be present in the second
component.
The free polyisocyanate constituent which can be employed comprises
any desired organic polyisocyanates having free isocyanate groups
attached to aliphatic, cycloaliphatic, araliphatic and/or aromatic
moieties. Preference is given to the use of polyisocyanates having
2 to 5 isocyanate groups per molecule and viscosities of from 100
to 2000 mPas at 23 degrees C.). If desired, small amounts of
organic solvent, preferably from 1 to 25% by weight are based on
pure polyisocyanate, may be added to the polyisocyanates in order
to improve the ease of incorporation of the polyisocyanate and, if
desired, to reduce its viscosity to a level within the
abovementioned ranges.
Solvents suitable as additives for the polyisocyanates are, for
example, ethoxyethyl propionate, butyl acetate and the like.
Examples of suitable isocyanates are described, for example, in
"Methoden der organischen Chemie", Houben-Weyl, Volume 14/2, 4th
edition, Georg Thieme Verlag, Stuttgart 1963, pages 61 to 70, and
by W. Siefken, Liebigs Ann. Chem. 562, 75 to 136.
Suitable, for example, are polyisocyanates and/or
isocyanate-functional polyurethane prepolymers which can be
prepared by reacting polyols with an excess of polyisocyanates and
which are preferably of low viscosity. It is also possible to
employ polyisocyanates which have isocyanurate groups and/or biuret
groups and/or allophanate groups and/or urethane groups and/or urea
groups and/or uretdione groups. Polyisocyanates which have urethane
groups, for example, are obtained by reacting some of the
isocyanate groups, with polyols, such as trimethylolpropane and
glycerol, for example. It is preferred to employ aliphatic or
cycloaliphatic polyisocyanates, especially hexamethylene
diisocyanate, dimerized and trimerized hexamethylene diisocyanate,
isophorone diisocyanate, 2-isocyanatopropylcyclohexyl isocyanate,
dicyclohexylmethane 2,4'-diisocyanate or dicyclohexylmethane
4,4'-diisocyanate, or mixtures of these polyisocyanates.
Very particular preference is given to the use of mixtures of
uretdione- and/or isocyanurate- and/or allophanate-functional
polyisocyanates based on hexamethylene diisocyanate, as are formed
by catalytic oligomerization of hexamethylene diisocyanate using
suitable catalysts. The polyisocyanate constituent may otherwise
also consist of any desired mixtures of the free polyisocyanates
mentioned by way of example.
In detail, the coating composition of the invention can
additionally comprise UV absorbers and free-radical scavengers. It
may also include catalysts for the crosslinking. Particularly
suitable for this purpose are organometallic compounds, preferably
organo tin and/or organobismuth compounds. Tertiary amine may also
be suitable. Furthermore, the coating composition can comprise
rheological agents and other coatings auxiliaries. It is of course
also possible for pigments of any kind to be present, examples
being color pigments such as azo pigments, phthalocyanine pigments,
carbonyl pigments, dioxazine pigments, titanium dioxide,
pigment-grade carbon black, iron oxides and chromium oxides or
cobalt oxides, or special-effect pigments, such as metal flake
pigments, especially aluminum flake pigments, and pearl luster
pigments. Furthermore, the coating composition of the invention may
if desired include further customary auxiliaries and/or additives,
examples being slip additives, polymerization inhibitors, matting
agents, defoamers, leveling agents and film-forming auxiliaries,
such as cellulose derivatives, or other additives which are
commonly employed in base coats. These customary auxiliaries and/or
additives are commonly employed in an amount of up to 15% by
weight, preferably from 2 to 9% by weight, based on the weight of
the coating composition without pigments and without fillers.
The coating composition of the invention is prepared by the
procedure of the invention, in which from 5 to 50% by weight, but
in particular up to 40, preferably up to 30, with particular
preference up to 20 and, in particular, up to 10% by weight of the
solids of a coating composition is substituted by at least one
polyol I to be used in accordance with the invention. For this
purpose the customary methods are employed, such as the combining
of the individual constituents and their mixing with stirring. The
preparation of the coating composition consisting of two or more
components takes place likewise by means of stirring or dispersion
using the apparatuses that are commonly employed, for example, by
means of dissolvers or the like, or by means of two-component
metering and mixing units that are likewise customarily
employed.
The coating composition of the invention is preferably formulated
as a nonaqueous solution or dispersion (i.e., with organic
solvents). For this purpose it is possible to use the organic
solvents that are customary in the preparation of coating
materials.
The binder mixture of the invention is preferably used to produce
single-coat or multicoat systems and, with particular preference,
to produce topcoats. Alternatively it can be used to produce a
clearcoat that is to be applied over a base coat film--for example,
a clearcoat of a multicoat system produced by the wet-on-wet
technique. In addition, it may also be used as a primer or
surfacer. The plastics with the other substrates can of course also
be coated directly with the clearcoat or with the topcoat.
Finally, the coating compositions can also be applied to other
substrates, such as metal, plastic, glass, wood or paper, for
example. Application takes place with the aid of customary methods,
for example, by spraying, knife coating, dipping or brushing.
The coating compositions can be employed for both the OEM finishing
and the refinishing of car bodies. They are preferably employed,
however, in the OEM finishing sector.
The coating compositions of the invention are preferably cured at
temperatures from room temperature up to 180.degree. C.
Particularly preferred temperatures are those between 60 and
180.degree. C. In specific forms of application of the coating
compositions of the invention it is also possible to employ lower
curing temperatures of from 60 to 160.degree. C.
The invention is described in more detail below with reference to
the examples:
EXAMPLE
TABLE 1 Composition of the novel (B, C) and of the conventional (A)
2-component system Composition A B C Constituents (parts by weight)
Component I Isocyanate 33 33.5 33.6 hardener.sup.a Component II OH
acrylate.sup.b 83.97 75 67.3 Oligomeric 4.5 9.0 polyol.sup.i TIN
384.sup.c 1.2 1.2 1.2 TIN 292.sup.d 1.0 1.0 1.0 DBTL.sup.e 0.004
0.004 0.004 Worlee.sup.R -ADD315.sup.f 0.096 0.096 0.096 ZN
73-1280.sup.g 1.5 1.5 1.5 Butylglycol 3.93 3.93 3.93 acetate Xylene
0.2 4.67 4.67 Solvent 3.2 naphtha GB ester.sup.h 4.5 4.5 4.5
Ethoxypropyl 2.0 2.0 2.0 acetate Butanol 1.6 1.6 1.6 Total 100 100
100 .sup.a 80% partial solution of Desmodur N3390 (polyisocyanate
based on hexamethylene diisocyanate, from Bayer) in butyl acetate
and solvent naphtha .sup.b customary and known acrylate resin made
from styrene, n-butyl methacrylate, t-butyl acrylate, hydroxypropyl
methacrylate and acrylic acid as acrylate resin (B) (diluted to 53%
solids content with a mixture of methoxypropyl acetate, butylglycol
acetate and butyl acetate) .sup.i oligomeric polyol I to be used in
accordance with the invention (characteristics: OH number 350,
viscosity 27.2 dPas at 23.degree. [cone-and-plate viscometer],
M.sub.n = 561, M.sub.w = 1068) .sup.c commercial light stabilizer
Tinuvin 384.sup.R from Ciba Specialty Chemical Inc. .sup.d
commercial light stabilizer Tinuvin 292.sup.R from Ciba Specialty
Chemical Inc. .sup.e dibutyl tin dilaurate .sup.f commercial
leveling additive from Worlee, D-Lauenburg .sup.g 5% strength
solution of a polyether-substituted polydimethylsiloxane in xylene
.sup.h glycolic acid butyl ester from Wacker
Composition A B C (parts by weight) Viscosity of component II (DIN
4 cup s at 23.degree. C.): 29s 22s 20.5s Solids content of
component I and II (1 h, 125.degree. C.) of processing viscosity:
53.6% 58.7% 60.5%
Performance Tests
1. BART Test (Chemical Resistance)
The BART (BASF ACID RESISTANCE TEST) is used to determine the
resistance of film surfaces to acids, alkalis and water drops. For
the test, the coating, after stoving, is subjected to further
temperature loads in a gradient oven (30 minutes at 40.degree. C.,
50.degree. C., 60.degree. C. and 70.degree. C.). Beforehand, the
test substances (1%, 10% and 36% strength sulfuric acid; 6%
strength sulfurous acid; 10% strength hydrochloric acid; 5%
strength sodium hydroxide solution; deionized water--1,2,3 and 4
drops--are applied in a defined manner with a metering pipette.
After the substances had been allowed to act, they are removed
under running water and the damage is assessed visually after 24 h
in accordance with a predetermined scale:
Rating Appearance 0 no defect 1 slight marking 2
marking/matting/softening 3 marking/matting/color change/softening
4 cracks/incipient through-etching 5 clearcoat removed
Each individual mark (spot) is evaluated and the result for each
coating is noted in an appropriate form (for example, total marks
for one temperature) The results are given in Table 1.
TABLE 1 Results of performance testing by the BART test Temp-
erature Composition A Composition B Composition C (.degree. C.) 40
50 60 70 40 50 60 70 40 50 60 70 H.sub.2 SO.sub.4 0 0 0 4.5 0 0 0
4.5 0 0 0 4.5 1% H.sub.2 SO.sub.4 0 0 0 4.5 0 0 0 4.5 0 0 0 4.5 10%
H.sub.2 SO.sub.4 0 0 0 4.5 0 0 0 4.5 0 0 0 4.5 36% HCl 0 0 0 2 0 0
0 2 0 0 0 2 10% H.sub.2 SO.sub.3 0 0 0 4 0 0 0 4.5 0 0 0 4.5 5%
NaOH 0 0 0 1 0 0 0 1 0 0 0 1.5 5% deion. 0 0 1.5 1 0 0 0 2 0 0 0.5
2 H.sub.2 O 1 deion. 0 0 0 2 0 0 0.5 2 0 0 0 2 H.sub.2 O 2 deion. 0
0 0 2 0 0 0.5 2 0 0 1 2 H.sub.2 O 3 deion. 0 0 0 1 0 0 1 1.5 0 0 1
1 H.sub.2 O 4 Total 0 0 0 20.5 0 0 0 21 0 0 0 21.5 acid Total 0 0
1.5 6 0 0 2 7.5 0 0 2.5 7 water
2. Sand Test (Scratch Resistance)
In the sand test, the film surface is subjected to sand (20 g of
quartz silver sand 1.5-2.0 mm). The sand is placed in a PE beaker
(base cut off flat) which is fastened firmly to the test panel.
Using a motor drive, the panel with the beaker and the sand is set
in oscillation. The movement of the loose sand damages the film
surface (100 double strokes in 22 s). After the sand exposure, the
test surface is cleaned to remove the abraded material, carefully
wiped off under a jet of cold water, and then dried with compressed
air. A measurement is made of the gloss in accordance with DIN
67530 before and after damage, at 20.degree. C.
This test procedure tests the resistance (scratch resistance) of
film surfaces (clearcoats and topcoats) to scratching from wash
brushes. The procedure is a good imitation of the stress undergone
by a film surface in a wash unit.
The results of the test are given in Table 2.
TABLE 2 Results of the sand test Composition Composition
Composition Gloss values.sup.a A B C Initial gloss 84 84 84
Residual gloss 53.5 55.5 56.5 Gloss after 55.3 58.1 60.2 2 h,
40.degree. C. Floss after 57.1 64.3 72.1 2 h, 60.degree. C. .sup.a
measured at 20.degree. C.
The results of the BART test on the one hand and of the sand test
on the other emphasize the fact that the novel two-component
systems (B and C) match the conventional two-component system (A)
in the high acid resistance and exceed it markedly in the scratch
resistance, especially in the reflow behavior at elevated
temperatures, and in the solids content.
* * * * *